Positive SV-40 Staining in Cases of Early PVAN without Nuclear Inclusions
Naima L Carter-Monroe, Serena M Bagnasco, Edward D Kraus, Lorraine C Racussen, Robert A Montgomery, Lois J Arend. Johns Hopkins University, Baltimore, MD
Background: Early histologic diagnosis of polyoma virus BK-associated nephropathy (PVAN) is hampered by lack of identifiable diagnostic viral nuclear inclusions on H&E stains. For these cases, pathologists rely on clinical suspicion of PVAN and/or histologic clues when deciding to order extra tests to demonstrate the presence of polyoma viral replication.
Design: We reviewed pathology reports for 43 renal allograft recipients with at least equivocal staining by SV-40 between 2007 and 2012 and assessed the presence of diagnostic nuclear viral inclusions in tubular epithelial cells (NI) on H&E, as well as the histologic pattern and viral load (VL). Histologic pattern score was based on the system described by Drachenberg et al, (pattern A: viral cytopathic changes with near normal renal parenchyma; patterns B1-B3: 3 levels of viral cytopathic change and tubulointerstitial scarring; pattern C: end-stage PVAN). Two additional patterns were added for cases with equivocal nuclear staining (E) or positive nuclear staining by SV-40 only (S), and evidence of tubulointerstitial scarring and/or inflammation without viral inclusions on H&E. VL was scored to assess the percentage of tubules exhibiting viral replication (1:<1%, 2:1%-10%,3:>10%), as described in the Banff working proposal for PVAN. An additional score of “0” was added for cases with equivocal SV-40 nuclear staining.
Results: A subset of 54 protocol and “for cause” biopsies were reviewed for 43 pts: 31 M, 12 F; 29 whites, 9 blacks, 5 other race; median age 51.4 years. Diagnostic viral nuclear inclusions were seen in 26 (48%) biopsies compared to 28 (52%) showing reactive/regenerative changes or atypia only. Cases without NI on H&E, but definite staining by SV-40, were more likely to have VL1 scores (32%), as compared to cases with NI (11%), with a significant trend towards higher VL scores (VL 2 or 3) in cases with NI (P<0.002). Cases without NI were more likely to exhibit histologic pattern E or S (n=27, 96%), whereas 22 (88%) of cases with NI demonstrated histologic pattern B1 and above. No cases demonstrated histologic pattern C. There was no significant difference between cases with or without NI with respect to the presence of inflammation or tubulitis.
Conclusions: Our analysis suggests that routine SV-40 staining may assist in the diagnosis of early stage PVAN in biopsies demonstrating lower viral loads and lack of diagnostic viral nuclear inclusions on H&E staining.
Category: Kidney (does not include tumors)
Monday, March 4, 2013 1:00 PM
Poster Session II # 224, Monday Afternoon